Curable compositions comprising epoxy resins and styrene have generally been epoxy-polyester compositions wherein a portion of the polyester is replaced with styrene or other ethylenically unsaturated monomer. See, for example, U.S. Pat. Nos. 2,691,077, 3,574,157, and 3,634,542.
Polyepoxide resin and styrene blends are also known. These blends generally exhibit poor processability, short pot life, high viscosity and cure with conventional curing agents to produce products which do not exhibit good physical properties; such as high heat deflection temperatures and retention of physical properties at elevated temperatures. See, for example, U.S. Pat. No. 2,939,859 directed to a polyepoxide/styrene blend cured with peroxides or amines. While the compositions of U.S. Pat. No. 2,939,859 do exhibit a reduction of viscosity over an epoxy composition alone, the resulting products do not exhibit high heat deflection temperatures.
Other patents covering polyepoxide/styrene compositions include U.S. Pat. Nos. 3,099,638 and 3,009,898, which are directed to the use of anhydride curing agents, optionally in the presence of a peroxide and/or tertiary amine accelerator.
It has now been found that epoxy/styrene blends can be cured to produce a two-phase system exhibiting unpredictably improved physical properties, especially increased heat deflection temperatures and excellent retention of physical properties, even at elevated temperatures, with a special amine-peroxide curing combination, optionally in the presence of certain plasticizers, promoters, etc.